Pneumatic tires are commonly assembled on cylindrical drums onto which successive belt-shaped strips of various uncured rubber materials such as tire tread stock are placed (sometimes called spliced) and must be securely joined (sometimes called stitched, consolidated or sealed) without curing, a process that overall may be called splicing. The assembled tire may go through additional manufacturing processes, at a minimum including placement into and vulcanization within an appropriate curing press. Thus, it is imperative that the strips be spliced sufficiently securely to insure their continued coupling throughout the remaining manufacturing process without curing the same.
Various methods have been utilized to accomplish splicing of such strips. For example, in U.S. Pat. No. 4,954,205 to Agawa, the ends of a belt of reinforcing ply including a plurality of reinforcing cords are mechanically forced into butt-splice engagement by a single rotatable wheel carried on an assembly that lowers the wheel into contact with the belt ends, moves it laterally thereacross, and raises the wheel. However, such a purely mechanical engagement likely does not produce a secure seal for various materials such as tire tread stock and is subject to separation during further manufacture.
Ultrasonics has been utilized to splice the ends of strips of various tire stock. In U.S. Pat. No. 3,904,457 to Laughlin multiple ultrasonic transducers which together span the width of a strip of reinforcing ply are placed into stationary engagement with the splice in the strip for a sufficient period to sonically weld the top seam of the splice. While this produces a secure seal, it requires a large number of moderately expensive ultrasonic transducers and may necessitate additional setup each time the width of the reinforcing ply is changed.
In U.S. Pat. No. 4,904,319 to DiVincenzo et al. a single ultrasonic transducer the width of a tread stock and having an engagement horn conforming to the profile of the tread stock is placed into stationary engagement with the splice in the tread stock for a sufficient period to sonically weld the top seam of the splice. This method also produces a secure seal and overcomes the expense of a great number of ultrasonic transducers. However, it requires manufacture of a unique and expensive horn for each tread stock profile. Also, manufacturing downtime and labor costs are incurred because the horn must be replaced with each change in tread profile.
A single ultrasonic transducer has been utilized to splice the ends of a strip of photographic film in U.S. Pat. No. 3,556,912 to Burgo et al. by lowering the transducer into engagement with the film splice, moving it laterally across the film along the splice, and raising it off the film. However, the unique characteristics of photographic film necessitated the inclusion of a set of pinch wheels having independent and relatively great freedom of motion to insure the film splice is fully sealed and is not skewed or damaged during operation of the transducer.